emission shader casting shadows - problem not solved
In your particular example case you could replace your emitter object with an area lamp - this does support suppressing shadows as shown :

3d View :


Cast Shadow disabled :


Cast Shadow enabled :


However, I don't think it's possible to suppress shadows from mesh-based emission materials due to the nature of the physics based rendering. ie, if you're suppressing light from emission surfaces then what about light reflected from a glossy surface - that could also cast shadows - as could light from a diffuse surface (albeit much more subtle, but it would still be a shadow).